The Jewish people of Jesus time knew from the OT Scriptures that righteousness was required to enter the Kingdom of God.
Jesus said the righteousness required was the very righteousness of God...his perfect righteousness (Matthew 5:48)
Part of the perfect righteous character of God was his gracious, compassionate heart...a heart of unconditional love, unmerited kindness, and unearned blessings.
The Hebrew word for gracious in the OT ischannun.
It is used 13 times in the OT to desribe the gracious, compassionate and kind heart of God.